Karenia brevis is an unarmored, non-peridinin-containing dinoflagellate that grows to ca. 20 to 40 μm in diameter. The organism is positively phototactic, is negatively geotactic, swims at a speed of ca. 1 m h−1 and is thought to be an obligate photoautotroph. K. brevis is the causative agent of the recurring red tide blooms (21 of 22 years from 1975 to 1997) observed in the Gulf of Mexico and off the southeastern Atlantic coast of the United States, which have been reported since the Spanish conquests. Lipophilic brevetoxins produced by K. brevis can result in massive fish kills and have been implicated in the mortality of 700 bottlenose dolphin off the east coast of the United States in 1987 and the mysterious deaths of 149 Florida manatees in 1995 and 1996. In cases of human exposure, brevetoxin can cause respiratory distress by inhalation and food poisoning by consumption of tainted shellfish.
Current methods for the detection of K. brevis depend on microscopy or pigment analysis, methods which are time-consuming and require a considerable amount of expertise and skill. Isolation of dinoflagellates and cultivation from environmental samples to confirm identity may take months. Consequently, rapid molecular methods to detect K. brevis in the environment are needed.